Patent GB-103344-A (GB)
Title: Improvements in and relating to Dynamo-electric Machines.
IPC: H02K17/38
Filed: 1916-01-26
Abstract: 103,344. British Thomson-Houston Co., and Shuttleworth, N. Jan. 26, 1916. Alternating - current motors; rotary converters and transformers. -- In the speed-regulation of an in-- duction motor A, Fig. 1, by means of a commutator machine C connected to its secondary winding B, the field-magnet windings E of the commutator machine are separately excited from a commutator frequency-changer H having slip-rings K connected to the supply and provided with two sets of commutator brushes P1, P2, P3 and Q1, Q2, Q3 movable in cpposite directions. The speed of the motor A is varied by altering the spacing of the pairs of brushes P1, Q1, &c. on the commutator; the power-factor of the motor A may be adjusted by rocking the whole of the brush gear bodily in one direction. The exciter H may be unprovided with a stator winding or with a stationary iron core; the exciter is mechanically coupled to the motor A when their pole-numbers are the same. An additional leading component of excitation may be introduced into the exciting- windings E of the commutator machine to assist the speed-regulation and powerfactor improvement of the motor A both above and below synchronism, and to enable the speed of the motor A to be taken through synchronism when under load. With this object, as shown in Fig. 2, the exciter H may be provided with an additional commutator winding and a second group of " magnetizing " brushes R1 S1, R2 S2, R3 S3, the mean position of the brushes R, S, being displaced ninety electrical degrees from the mean position of' the "speed-regulating" brushes P, Q1, and the other brushes being similarly displaced. The brush-pair R, S1 is connected in series with the brushpair P1 Q1, and the resultant voltage is impressed on one phase of the exciting-winding E, similar connexions being made for the other phases. The speed of the main motor is varied by adjustment of the brushes P, Q1 &c., and its power-factor is corrected by adjustment of the brushes R1 S, &c. To enable the main motor to pass through synchronism without any shifting of the brushes R1 S, &c., the primary winding A, B, Fig. 3, of a transformer is connected across each pair of '' magnetizing " brushes R1 S1 &c., and the secondary winding C, D of the transformer is connected in series both with the primary winding and with the exciting-winding E, but is wound in the opposite sense to and possesses a larger number of turns than the primary winding. The windings for the three phases may be carried on a single closed transformer core having three legs. The exciter brushes may be moved by means of a pinion 0, Fig. 4, on the shaft of a hand-wheel engaging toothed racks M, N, the rocker for the brushes P1, P2, P3 carrying one rack, and the rocker for the brushes Q1, Q2, Q3 carrying the other rack. In the case of rolling-mill equipments employing fly-wheels, the brushes may be shifted automatically by means of a solenoid 7, Fig. 6, excited by a current proportional to the primary or secondary current of the induction motor. The solenoid plunger is attached to one end of a chain 6 passing over a sprocket-wheel 5 on the shaft of the pinion O, Fig. 4, the other end of the chain being fixed to a spring 8. The speed of the main motor is preferably kept constant up to full load and caused to drop rapidly on overloads by providing on the chain 6 a tray 9 on which weights are placed. Specifications 1457/07 and 5260/15 are referred to.